Voice over Internet Protocol (VoIP) systems provide voice communications over a digital network, such as an Internet Protocol (IP) network. In conventional systems for providing VoIP service, conventional telephones (analog phones) may be connected to local site wiring through a terminal adapter at each telephone. Alternatively, a VoIP telephone may be used without a terminal adapter. A local network adapter converts the signals received from the local site wiring to digital data communications and forwards the communications over a broadband connection, such as a Digital Subscriber Loop (DSL) connection, to a central location. Data from the central location is received over the broadband connection by the local network adapter, converted to the appropriate signals for the telephones and forwarded on the local site wiring to the telephones.
Power for the VoIP service is, typically, provided at the local site. As a result, if power is lost at the local site, the network adapter may no longer operate and telephone service may be unavailable. Likewise, if there is a problem with the broadband connection, either at the local site or at the central location, telephone service may be lost.
A conventional technique to avoid loss of telephone service is to provide a public switched telephone network (PSTN) service that is connected to the local site wiring. In the event of a failure of the VoIP service, a user would, typically, unplug the terminal adapter and connect a conventional analog telephone to the local site wiring to access the PSTN service. Typically, analog telephones would not be directly connected to the local site wiring prior to the failure because such telephones may then use the PSTN service rather than the VoIP service even when the VoIP service is available.